Just need a math check here.

If I have a pump that draws 1.07 Amps on  a 220 volt service.   This = 235 Watts

If this pump runs 160 hours, then this is   37.6 Kwh.  If I pay $.07 per Kwh then the cost to run the pump is  $2.63.


Am I doing this right?  Want to make sure before I make a fool of my self.

your math is right , in fact an over estimation , with out a PF or a watt meter we can only get KVA and not KWH could be right on could be 40% high

The only mistake you have is that it's 240V, not 220. This will increase the numbers a little. Measure the voltage anywhere on a 240 system. It usually ranges from 236 to 244, from what I've seen.

there are allot of 220V homes out there , grid fluctuations are 10%

It's my understanding that on a small load such as this, in a residential setting, PF won't play a role, or if so, it's completely negligible.

your 100% right but as a rule you cant assume volt times amp = Watt
the difference in the $ is a penny or 10

Definitely need to factor PF

Good news is your estimate without it will always be correct or high.

Comments about 240 vs 220 are valid as well - as far is I know / have experienced, grid voltage is 120 / 240 these days. 110 / 220 may be a relic of decades past.

A P3 Kill-a-Watt, available from Amazon for ~$25 is a nifty gizmo for learning about VA, PF, etc for plug loads. Not usable for 240 V loads though.

Smaller loads often have crappy (well below 1.00) PF, and it is negligible as to effect on grid as Clark notes, but for purpose of knowing cost of operation of a small load run for hours and hours, must consider PF. Evaluating alternatives based upon estimated cost of operation calculated from Volts X Amps may result in a flawed analysis since the load with low PF costs less to run than the VA calculation suggests.

Hope this helped.

How then does one determine the PF on Dewayne's pump load?

I think that you need to use an oscilloscope, and measure the phase difference between the voltage trace and the current trace.

There are instruments for gathering 240 Volt device PF, VA, etc. I don't know of anything cheap.

Maybe pump mfg could supply PF?

I suppose one could jerry-rig a bench tester using two Kill-a-Watts, one on each hot leg, tie neutrals together. Could work for 240 V loads up to 15 Amps.

Could also wind up letting factory installed smoke out of pump or Kill-a-Watts, so make it a fire-resistant bench

kind of off topic a little, but i wonder if those KVAR units for sale on fleabay actually do anything. we run 1000's upon 1000's of horse power of induction motors where i work, we use huge banks of capacitors to help correct PF, they save us thousands of $$$, we have a few syncronis motors that help as well.

Only if you get charged in KVAH
and if you do dont go off the shelf correcting for PF should be done for each peice idividualy
there is a link on a thread here that goes quite in depth on correcting PF
doesnt change watts , decreases amps